1. Field of the Invention
The present invention relates to an erroneous package mounting determination method for a transmission device, and a transmission device employing this method. In particular, the present invention pertains to a method whereby erroneous package mounting is determined for a transmission device which can mount packages, each of which has transmission circuits corresponding to a plurality of transmission speeds.
2. Related Arts
Recently, as one consequence of the development of the information society, the societal importance of networks, as well as the scale of networks, constructed using transmission devices has increased, and there has been a corresponding increase in the quantity of information handled. As a result, an improvement in the reliability and the safety provided by networks is urgently desired.
In this situation, transmission devices having multiple packages mounted in a device frame have come to be employed. And for this reason, the employment of a faulty package mounting operation, i.e., the erroneous mounting of packages, will result in the cutoff of an operation line, or the like, and in the occurrence of a critical obstacle to the effective use of an application by clients.
Therefore, a transmission device is desired which is designed while taking into account a fail-safe process permitting the mounting of packages with minimal, or no, damage being incurred by erroneous package mounting.
In accordance with this desire, a conventional method for attaching a label to a package (hereinafter referred to as an IF board) to prevent erroneous mounting is provided as a first technique whereby the erroneous mounting of an IF board can either be prevented or visually discerned.
According to this method, labels describing the name of an IF board, a diagram number, and the name of a mounting device are attached to an IF board, so that a worker can ascertain visually whether an IF board should be mounted on a specific device. With this method, whether or not an erroneous mounting incident occurs depends on how attentive to detail a worker is.
A second technique is a method by which whether an erroneous mounting has occurred can be determined using an IF board ID. FIG. 34 is a diagram for explaining the arrangement of a transmission device which employs this method. A transmission device 1 includes a processor 2, a plurality of IF boards 5, a comparator 11, a memory 10, and a display unit 12. The IF boards 5 each carry IF board type identification information inherent to individual IF board types (hereinafter referred to an IF board ID).
This information is stored in an IF board ID storage unit 51 mounted on each of the IF boards 5. In the memory 10 are stored data concerning mounting slots in the device, and a pair of IF board IDs for IF boards to be mounted in the slots.
With this arrangement, the determination of whether a board has been erroneously mounted is performed as follows. When an IF board 5 is mounted in a specific slot, the processor 2 acquires the IF board ID from the IF board ID storage unit 51 on the mounted IF board 5, and the processor 2 acquires from the memory 10 the IF board ID for an IF board which should be mounted in the slot.
Then, the IF board ID acquired from the mounted IF board 5 and the IF board ID for the IF board which should be mounted, acquired from the memory 10, are input to the comparator 11. When as a result of the comparison by the comparator 11 it is found that the two IF board IDs match, it is ascertained that the IF board 5 is correctly mounted. Whereas, if the two IF board IDs do not match, it is ascertained that the IF board 5 is erroneously mounted.
A third technique is a method whereby an erroneous mounting is determined by using a difference between the terminal positions of an IF board. FIG. 35 is a diagram for explaining this method. A transmission device 1 includes IF boards 5, slots 13 and a processor 2. Each IF board 5 includes an identification terminal 52 and an IF board internal loop 54. Each slot 13 includes identification terminals 131 and a common terminal 132.
The common terminal 53 and the identification terminal 52 on the IF board 5 are connected to form a loop, with the position of the identification terminal 52, which is one end of the loop, differing with the IF board type. The common terminal 132 is used in common by all the slots 13, and is connected to the processor 2. For the individual slots 13, only the identification terminals 131 corresponding to the IF board types which are normally to be mounted are connected in parallel to the processor 2.
In the arrangement shown in FIG. 35, the process for determining an erroneous mounting is performed as follows. First, the processor 2 transmits a common signal 14 to the common terminals 132 of all the slots 13. For the slots 13 in which the IF boards 5 are normally mounted, the common signal 14 passes trough the loops 54 in the IF boards 5 and the identification terminals 52 and returns to the processor 2 (IF boards 1 and 2 in FIG. 35).
For the slots 13 in which the IF board is erroneously mounted, the IF board 5 and the identification terminals 52 of the slot 13 are rendered nonconductive, and no signal returns to the processor 2 (IF board 3 in FIG. 35).
When the common signal 14 is transmitted in the above described manner, a signal which passes from the identification terminal 52 to the processor 2 is defined as an identification signal 15. Whether or not an IF board is erroneously mounted in a slot can be determined by conducting an examination to detect the presence of such a signal.
A fourth technique is a method whereby erroneous mounting is prevented by employing IF boards having different shapes. According to this method, the shape of a connector on an IF board, or the position of the connector, varies depending on the IF board type, so that an IF board of an incorrect type can not physically be inserted into a slot.
However, the above described conventional erroneous mounting determination methods have the following shortcomings.
Regarding the first conventional technique, it is impossible for errors to be completely prevented when human labor is a factor. The safety required as an operating countermeasure for the erroneous mounting of an IF board can not be ensured. Although the second to the fourth conventional techniques are effective when one-to-one correspondence is established for the slots and normally mounted IF boards, these methods can not be applied when IF boards to be mounted comprise a plurality of types having configurations which correspond to a single slot type.
When the third and the fourth conventional techniques are employed the alteration of hardware is required, and therefore, these techniques are not suitable for saving space of the device and reduction of manufacturing costs.